This application relates to an improved seal for a connection between a driver plate and its associated rubber cushion in a starter motor drive assembly.
In the prior art, start motors are utilized to initiate turning a vehicle engine. An electric motor drives a pinion, which engages a ring gear. Upon rotation of the ring gear, the engine is turned to begin operation of the engine. At the same time, other components act to start the engine to be self-running.
In one known type of starter motor, the pinion gear is associated with the electric motor and is brought selectively into contact with the starter motor ring gear upon start-up of the electric motor. The electric motor has a drive shaft which rotates a drive plate spaced on an opposed side of the pinion from the side gear. A rubber cushion is positioned to connect the drive plate to the pinion. The drive plate is mounted on threads on the drive shaft. Upon start-up of the electric motor, the pinion is rotated. The pinion, rubber cushion and drive plate all move on the threads on the shaft such that the pinion engages the ring gear. Once the pinion engages the ring gear, the drive plate continues to move on the threads, and compresses the rubber cushion between the drive plate and the pinion. As the rubber cushion becomes compressed, the amount of torque transmitted from the shaft to the pinion increases due to the drive plate approaching the pinion, and the drive plate beginning to transmit a portion of the torque.
The above-described general operation for a starter motor is known in the art, and has achieved wide success. However, there are challenges with this design. The interface between the drive shaft and the drive plate, and in particular, the threaded connections, are greased. If there is too much grease placed at the interface, the grease will sometimes migrate into the area between the drive plate and the rubber cushion. This is undesirable, and can affect the connection between the drive plate and the rubber cushion. Moreover, the contaminants, such as water, oil, dust, etc., can move into the area between the drive plate and the rubber cushion. This is undesirable.